中文摘要：

用分子动力学方法模拟二维颗粒系统在水平振动下的分离现象，通过数值模拟发现，在固定的振幅下，存在使得分离效率最佳的振动频率，在固定的振动频率下，也存在一个使得分离效率最佳的振幅。根据模拟结果，给出了最佳振幅对振动频率的经验公式。同时，还指出了存在两种不同的分离机制，当振动的加速度过大时，处于垂直边界附近的大粒子会通过容器的边界直接被抛到最顶部。

英文摘要：

The size segregation of grains is studied with two-dimensional molecular dynamic simulations for dissipative particles under horizontal vibration. A series of segregation that induced by horizontal vibrations at different amplitudes and frequencies are reported and the relationship between these two aspects is analyzed. A standard is given to scale the speed of the segregation. It is found that an optimal amplitude exists at a given frequency. An empiristic formula is obtained for this amplitude. It shows that another segregation mechanism exists at a large amplitude and frequency, in which the big particles are thrown directly to the top by the side wall.